Inaudible inflight announcements. Many times it is very difficult to hear the announcements on the plane. A couple of times I've asked a flight attendant what the announcement was, and they said it was about duty free sales or some such. One time they were giving connecting gate information, and I could only catch parts of it. Another time, on taxi out, we heard several loud bangs, an unintelligible announcement was made, and we returned to the gate. It turns out that we had a compressor stall, and they were going to locate another aircraft for us. But I didn't know this until I pressed my call button so I could ask a flight attendant. What if it were a real emergency and we couldn't hear the announcements? We wouldn't have any idea what was going on. By the way, there is nothing wrong with my hearing.